Little is known of the epidemiology of osteoporosis, falls and fractures in Hispanic-Americans. The proposed study would recruit 150 Mexican-American women in the age range 65-84 years from San Mateo and Santa Clara Counties in northern California, and would focus on the epidemiology of bone mineral density and of falls. Particular emphasis is given to the role of physical frailty and environmental, cultural, and nutritional factors in the causation and progression of low bone mineral density and falls. A baseline cross-sectional study would include the following measures: bone mineral density in the hip, spine, distal radius, proximal radius, and whole body calcium; frequency of falls in the past year (by questionnaire); biochemical markers of bone turnover; skin pigmentation; tests of muscle strength, gait, mobility, and balance; and (by questionnaire) information on a variety of other putative risk factors for low bone mineral density and for falls. Study subjects would have the same measurements repeated annually for four years. The baseline cross-sectional survey would provide data not currently available on the distribution of bone mineral density, fall frequency, and other indicators of physical frailty in Mexican-- American women in this age group, and on factors correlated with bone mineral density and on characteristics of women who fall. The longitudinal component would allow identification of predictors of bone mineral density and fall frequency, as well as predictors of change over time in bone mineral density; markers of bone turnover, and fall frequency. Thus, this study should provide new information on the frequency of low bone mineral density and of falls, and of the roles of physical frailty and other factors in the etiology Mexican-American women.